Introduction
Typical coal refuse thickener feed to a settling tank contains considerable amounts of inorganic gangue, clays and the like. These materials have previously been pulverized and dispersed in water and present a difficult problem in regards to the recovery of coal values therefrom. In most instances, no attempt is even made to recover the coal in the refuse or reject. As a result, the coal is lost. The coal content in the refuse can range from 25 to 70% (based on the weight of refuse solids). Simply adding flocculants to this slurry provides flocculation for both coal particulate matter as well as particulate matter obtained from inorganic gangue, clays and other suspended materials present in these slurries, such that separation of the coal values is not possible.
If it would be possible to selectively flocculate the coal from such a pulverized coal refuse slurry, an advance in the art could be achieved.
We have discovered that we can selectively flocculate the coal from such a pulverized coal refuse aqueous slurry by the use of special flocculants which then cause the selective flocculation and settling of coal particles while leaving inorganic gangue, clays and like materials preferentially suspended in the aqueous phase.
Applying standard solid/liquid separation techniques in this selectively flocculated coal then provides for the recovery of a concentrated, flocculated coal slurry whose ash value is appreciable lower than the original coal refuse ash value and provides for the recovery of dispersed clays, inorganic gangues, and the like with recycle of waters possible which may derive additional economic benefit to the operator.
It is the object of this invention to selectively flocculate coal values from a dispersed pulverized coal refuse slurry which contains pulverized coal and inorganic gangue, clays and the like. A clay like inorganic gangue material dispersed in water may then be subsequently settled and collected, and the water values recycled back to the mining operations.
It is also an object of this invention to recover a low ash particulate coal from a pulverized coal refuse slurry containing high ash inorganic gangues, clays and the like.